Chapter 15- Senses (reduced version Flashcards
Five Special Senses
- Vision
- Olfaction
- Gustation
- Hearing
- Equilibirum
Conjunctiva
Transparent mucous membrane
produce lubricating mucus
palpebral conjunctive
portion that covers the inner eyelids
bulbar conjunctive
portion that covers anterior surface of the eye (except the cornea)
Palpebrae
eyelids
orbicularis oculi
encircles the eye
eyes closed when it contracts
levator palpebrae superioris
upper eyelid
eye opens when it contracts
lacrimal caruncle
on medial portion
sebaceous and sweat glands here produce oily secretion
lacrimal apparatus
production and drainage of tears, protection of eyes
lacrimal apparatus is composed of
lacrimal gland- produces and releases dilute saline solutions
lacrimal canaliculi- drains tears from eye surface at medial portion of eye
nasolacrimal duct- drains tears from lacrimal canaliculi into nasal cavity
fibrous layer
outermost coat of the eye with 2 regions - sclera and cornea
vascular layer
middle coat of the eye with three regions - choroid, ciliary body, iris
ciliary body (3)
muscle- smooth muscle bundles that control lens shape
processes- secrete aqueous humor
suspensory ligaments- extend from ciliary processes to lens
retina
innermost layer of the eye (2) - pigmented late lies against the choroid) and the neural layer (innermost layer of the retina that contains rods and cones - and bipolar and ganglion cells)
Optic Disc
Point at which the optic nerve exits the back of the eye
Macula lutea
area where other structurd are displaced - photoreceptors receive direct light
fovea centralis
center of the fovea
contains only cones
only 1/1000th of the total visual field
lens
biconvex
transparent
flexible
used to bend light as it enters the eye
lens epithelium
anterior portion covered by this
coordinates metabolic activities of lens
provides more cells for lens fibers
lens fibers
Bulk of lens thickness made up by this
old fibers never broken down - causes cataracts
loses its flexibility
Anterior segment
Front of the eyes
Contains aqueous humor
Supploes nutrients and oxygen to structure in the front of the eye and removes waste
constantly drained and produced
becomes a problem when it pushes on the optic nerve and the retina and they wont function normally
posterior segment
found behind the lens
contains vitreious humor
transmits light, stabilizes the lens from the posterior side, holds the retina in place and contributes to intraocular pressure
lasts a lifetime
visible light spectrum
400-700 nm
human eyes response to electromagnetic radiation
White
all wavelengths of light reflected
black
all wavelengths of light absorbed
refraction
when a light wave passes through a boundary from one medium to another with a different density
focal point
light rays bend so they converge at a single point
real image
upside down and reversed and then flipped by the primary visual cortex
ways light is bent
- cornea
- anterior surface of the lens
- posterior surface of the lens
changing lens shape
relaxation of ciliary muscle - pulling of suspensory ligaments (flat lens)
OR
contraction of ciliary muscle - decreased pulling in suspensory ligaments (bulge lens)
far point of vision
point at which the lens no longer needs to change shape to focus light (20 ft)
paralleled light rays are easier to focus
near point of vision
closest point to the face that still allows clear vision (4 ft)
Accommodation of the lens
contraction or relaxation of ciliary muscles
Constriction of pupils
prevents divergent rays from entering the eye
convergence of eyes
medial rotation of the eyeballs
keep objects focused on the fovea
Outer segment of rods and cones
embedded in pigmented layer of retina
contains photopigments folded into discs
Inner segment of rods and cones
embedded in the neural layer of retina
Rods
Sensitive to light
Used in low light conditions (dark)
Only one visual pigment in rods → no color vision
More photopigments
Ganglion cell will synapse
cones
Low sensitivity
Overlapping wavelengths of light that are stimulating different
Used more in bright light color vision
Single cone has 1 of 3 (red, green, or blue) visual pigments → color vision
Each cone synapses on its own ganglia
visual clarity
Phototransduction
Process of converting light energy into a graded receptor potential that begins when a photoreceptor catches light
Photoreceptor cells
create graded potential in response to incoming light stimuli
bipolar cells
create either IPSP or EPSP
ganglion cell
generate action potential that is propagated along the optic nerve and sends the info to the primary visual cortex
Dark
Photoreceptor io channels are open
receptor is depolarized to -40 mV
Light
Photoreceptor ion channels are closed
receptor is hyperpolarized to -70 mV
process uses transducin signaling system
transducin
11 cis retinol absorbs light and becomes all trans retinol
cgmp to gmp
Information processes in the dark
- photoreceptor- depolarizes to -40 mV
- bipolar cell- ipsp
- ganglion cell- hyperpolarizes to -70 mV - no action potential generated
Information processes in the light
- Photoreceptor- hyperpolarizes
- Bipolar- depolarizes
- Ganglion- depolarizes; If strong enough, generates action potential
Light Adaptation (reduced)
rods off
sensitivity low
nright lights takes 60 seconds
highest visual acuity at 5 mins
dark adaptation (reduceD)
rods on
sensitivity high
takes 30 minutes
optic tracts (3)
continue to the visual cortex
1) Carries fibers from the lateral portion of the eye on the same side
2) Carries fibers from the medial portion of the eye of the opposite side
3) Contains all information from the same half of the visual field
Medial portion of eye receives input from BLANK part of the visual field
temporal
lateral portion of eye receives input from BLANK part of the visual field
medial
lateral geniculate nucleus
most fibers i optic tracts synapse with neurons here - go to primary visual cortex
other fibers travel to
- superior colliculi - visual reflex center controls extrinsic eye muscles
- pretectal nuclei - mediates pupillary response to light
- suprachiasmatic nucleus - biorhythms
Depth perception (reduced)
each eye has a visual field of 170
allows ability to locate objects in space
Olfaction
Chemoreceptors respond to stimiuli dissolved in solution
olfactory epithelium
the roof of the nasal cavity
anything you see on the outside of the body plays no role in smelling
3 cells tyopes of olfaction
1) Olfactory sensory neurons
2) Supporting cells
3) Olfactory stem cells
Olfactory cilia
hair-like projections found in olfactory epithelium
increase receptive surface area of neuron
More able to pick up smell and smell it
Mucus surrounding cilia dissolves airborne odorants
no mucus - Not going to smell it
Filaments of hte olfactory nerve
travel through ethmoid bone via cribriform foramina
Mitral cells
Axons synapse with these
creates action potential for perception of smell
Glomeruli
cluster
site of the mitral cells synapsing in the brain
How are olfactory sensory neurons destroyed?
Some smells are particularly noxious and destroy the neurons - people who work in orgo labs long term will lose their sense of smell
Life span of olfactory sensory neuron → 30-60 days
Olfactory stem cdells
replace damaged/destroyed neurons bc you dont want smell to be gone forever
What two things ust take place for sensation of smell to occur
- activation of sensory neurons (binding of oderant in the olfactory cilium membrane)
- transduction of smell (graded potential is created due to the binding and stronggraded = action at the mitral cell)
Transduction of smell
involves G-protein
Na+ influx depolarizes olfactory sensory neuron → creates receptor potential
Ca2+ influx causes adaptation → decreased response to sustained odorant stimulus
Pathway to the Olfactory CortexGus
- olfactory bulb
- synapse with mitral cell
- graded potential = action potential
- impulses from bulb through olfactory tract
TWO PATHWAYS - a. olfactory cortex- smell consciously interpreted/identified
b. limbic system- smells elicits an emotional response
Gustation
chemoreceptors are on taste buds on papillae of tongue (grainy texture)
3 types of papillae
fungiform- found all over the tongue
Vallate- back of the tongue
foliate- side of the tongue
Gustatory epithelial cells
receptor cells for taste
gustatory hairs
microvilli projecting from tips of gustatory epithelial cells
increase surface area
receptor membrane of gustatory epithelial cells
sensory dendrites-
forms first part of pathway to the brain
basal epithelial cells
replace lost or damaged gustatory epithelial cells
replace every 7-10 days bc cells get scraped off
six taste modalities
sweet - sugars, alcohol
sour- acids
umami- amino acids glutamate and aspartate
salty-metal ions
bitter - alkaloids
long-chain fatty acids - lipids
1 modality
single taste cell per each modality
Stimulating multiple types of gustatory cells at the same time with combinations
Taste perception process (2)
- activation of taste receptors
- transduction of taste
transduction of taste
- salty - Na influx
- sour - H influx
- bitter/sweet/umami- gustducin
Cranial nerves involved with taste
facial nerve- innervates 2/3rds of the anterior tongue
glossopharyngeal nerve- 1/3 posterior tongue
pathway of fibers for gustatory
synapse at solitary nucleus in medulla, travel to primary gistatory cortex
importance of taste
likes and dislikes
cravings = short on nutrition
some tastes indicate spoiled food or poison
Pharyngotympanic tube
opening of tube equalizes pressure in the middle ear
tympanic membrane only vibrates if pressure is equal on either side (inside and outside the body)
Source of an ear infection (otitis media)
bony labyrinth
system of channels that weave through the temporal bone
perilymph
fluid similar to CSF
surrounds & supports the membranous labyrinth
Membranous labyrinth
membranous sacs and ducts found within the bony labyrinth filled with endoluymph which is fluid similar to ICF
surrounds sensory cells in ear and transmits sound and allows for balance
cochlea
spiral chamber of hte inner ear
Cochlea ends blindly at the BLANK
helicotrem - produces nerve impulses in response to sound vibrations
COCHLEA division
- scala vestibuli - begins at oval window
- scala tympani- has vestibular membrane (wall that divides s media from s vestibuli), stria vascularis (secretes emdolymph) and basilar membrane (forms floor of s media)
- scala media- cochlear hair cells and supporting cells
sound
mechanical waves
result from vibration of particles of medium through which sound is travelling
compression (air polecules pushed together)
rarefaction (air molecules spread apart)
Frequency
pitch
number of sound waves that pass a point in a given period
wavelength
distance between crests of a given sound wave
shorter wavelength = higher freuqnecy
tone
sound consisting of a single frequency
amplitude
loudness
higher crest = more pressure = louder
human hearing
above 120, sound is painful
Sound transmission
- vibrate tympanic membrane
- malleus , incus and stapes vibrate too, and stapes send info through oval window to middle ear
- oval window movement = scala vestibule peeriluymph to move and push waves to helicotrema
round window is pressure valve
if through round window - sent to cochlea
4 a. helicotrema path - low frequency (<20 Hz) pass completely around helicotrema to round window (cant hear this)
b. Basilar membrane path- sounds waves transmitted through scala media and pressure waves vibrate the basilar membrane (hear something bc its over 20 hz)
Fibers in basilar membrane
near oval window- short and stiff (inflexible)
high frequency
near helicotrema- long and loose
low frequency
sound transduction
Movement of the basilar membrane stimulates inner hair cells
Inner hair cells have hair-like projections called stereocilia
Tallest stereocilia embedded in tectorial membrane
Stereocilia joined by tip links
Tip links connect to mechanically gated ion channels → pulling tip links opens ion channels
Trap door=
if open, ions can freely float into the hair cell
If closed, no ion flow into hair cells
When basilar membrane is at rest:
Some tip links open - small amount of ion flow
Inner hair cell slightly depolarized
slight action potentials
When stereocilia pivot toward tallest hair:
Tip links open - all ion channels open
Inner hair cell depolarizes = creates receptor potential
high action potentials
When stereocilia bend toward shortest hair:
Tip links close
Inner hair cell hyperpolarizes
Neurotransmitter no longer released
No action potentials at all
Outer hair cells
change the flexibility of the basilar membrane
1. increase responsiveness of inner hair cells (Easier to move = easier to stimulate inner hair cells)
2. Protection (outer hair cells stiffen in response to loud sound) and decreases the flexibility of the basilar membrane and makes it more stiff to protect from loud sounds
Pathway to the Primary Auditory Cortex
Fibers from cochlear nerve project to superior olivary nucleus
Received by both the left and right side of the brain even if occurring on the opposite side of the body
Localization of sound
Intensity and timing localize sound source
if identical (up down front back) or if different (left or right)
Equilibrum (2)
Vestibule- saccule (continuous with cochlea) and utricle (continuous with semicircular canals) both contain maculae receptors that respond to linear acceleration and head position
Semicircular canals- anterior (flip), posterior (cartwheel) lateral (spin)
semicircular duct passes through each canal
ampullae swells at the end of each duct with receptor crista ampullares and responds to rotational movement
Stereocilia, kinocilia are longest
Flat patch with supporting cells + hair cells
Otolith membrane
jelly-like base with small otolith stones embedded in membrane (dense and move)
why vertigo happens
Bending toward kinocilium
hair cells deplarize
bending away from kinocilium
hair cells hyperpolarize
utricle
maculae are horizontal
hair cells are verticle
forward and backward movement
saccule
maculae are verticle
hair cells are horizontal
up or down movement
maculae
respond to changes in head position
Ampullary cupula
gel that surrounds hair cells
Sensation of Rotational Movement
Endolymph flows through canals in opposite direction as rotational movement
Hairs deflected → depolarization occurs, increased neurotransmitter released
Consistent speed of rotation → endolymph travels at same speed as rotation means hair cells not stimulated
Stop rotating → endolymph flows in opposite direction
Hair cells hyperpolarize → less neurotransmitter released
Pathway to vestibular nuc;ei or cerebellum
info sent to reflex centers of the brain automatically
vestibular nuclei- major integrative area for balance and Sends impulses to brain stem -information used to correct body position
2. cerebellum- coordinates skeletal muscle activity and muscle tone to maintain head position, posture, balance
Maintaining head position as well
